[Asterisk-Users] Routing 911 calls

[Matt]

Has anyone used asterisk as a simple voip server? (I'm sure its been/ing done).
If so... how did you provide 911 service?   Did you setup different
contexts and put sip phones in those contexts per county?

Also, is it possible to put a phone into multiple contexts?

For instance:

context=from-internal

Can I add a second context like with a , comma?  So the phone can have
the rules from 2 contexts?  How would I do that?